1. Field of the Invention
This invention relates to a light-emitting material capable of converting electric energy to light (luminescent element material) and a luminescent element comprising the same. More particularly, this invention relates to a luminescent element (device) suited for use in the fields of display elements, displays, back lights, electrophotography, lighting sources, recording light sources, reading light sources, labels, signboards, interior decorations, and the like.
This invention also relates to an ethylene derivative having a nitrogen-containing 7-membered ring which is useful as a charge transporting compound in an electrophotographic photoreceptor, an organic electroluminescent element, etc.
This invention also relates to a benzoazepine derivative having a vinyl group, which can be a raw material of polymer useful as an electrophotographic photoreceptor, an organic electroluminescent element, etc.
2. Description of the Related Art
Today various display devices have been researched and developed. Inter alia an organic luminescent element has been attracting attention as a promising means for obtaining electroluminescence of high brightness at a low driving voltage. For example, a luminescent element comprising an organic compound in a thin film formed by vacuum evaporation (see Appl. Phys. Lett., vol. 51, p. 913 (1987)). However, production of an organic luminescent element involving vacuum evaporation of an organic compound has a problem of productivity. From the standpoint of simplification of production process, processability, and increase of a display area, production of an organic luminescent element by a coating system is desirable.
Known luminescent element materials useful in the production of luminescent elements by a coating system, which is advantageous for productivity, include π-conjugated polymers typically exemplified by p-phenylenevinylene. However, having a light-generating part in the polymer main chain, the π-conjugated polymers have difficulty in controlling concentration so that it is difficult to delicately control the color tone and luminescent intensity.
Luminescent elements prepared by the coating system also include those comprising a low-molecular fluorescent compound dispersed in poly(N-vinylcarbazole) (JP-A-4-212286). Because this mode permits free alteration of the fluorescent compound species, it is relatively easy to control the color tone and luminescent intensity. However, the luminescent elements of this mode require a high driving voltage and involves a problem of durability such that the brightness tends to decrease when the element resumes operation after long suspension or when the element is operated continuously.
Photoconductors that have been used in electrophotographic photoreceptors chiefly include inorganic substances such as selenium, cadmium sulfide, and zinc oxide. Electrophotographic photoreceptors are essentially required (i) to be charged in appropriate positions thereof in the dark, (ii) to hardly dissipate the charges in the dark, and (iii) to be able to dissipate the charges quickly upon being irradiated. Photoreceptors comprising the inorganic photoconductors possess many merits and demerits. For example, the demerits of widely used selenium photoreceptors, while well satisfying the requirements (i) to (iii), lie in (1) strict conditions of production, which leads to a high cost of production, (ii) lack of flexibility, which makes it difficult to obtain a belt photoreceptor, and (iii) sensitiveness to a thermal or mechanical shock, which necessitates careful handling. While cadmium sulfide and zinc oxide have been used as dispersed in a binder resin, they cannot withstand alone repeated use due to their mechanical drawbacks in terms of smoothness, hardness, tensile strength, and abrasion resistance.
To solve these problems, electrophotographic photoreceptors comprising various organic photoconductors have recently been proposed, and some of them have been put to practical use. Organic photoreceptors so far developed include one comprising poly-N-vinylcarbazole and 2,4,7-trinitrofluoren-9-one (U.S. Pat. No. 3,484,237), one comprising poly-vinylcarbazole sensitized with a pyrylium salt dye (JP-B-48-25658), one mainly comprising an organic pigment (JP-A-47-37543), one mainly comprising an eutectic complex of a dye and a resin (JP-A-47-10735), one mainly comprising a hydrazone compound (JP-A-57-101844 and JP-A-54-150128), one mainly comprising an aromatic tertiary amine compound (JP-B-58-32372), and one mainly comprising a stilbene compound (JP-A-58-198043). Although these photoreceptors exhibit excellent characteristics and appear to have high practical values, they are not fully satisfactory taking the latest various requirements for photoreceptors into consideration. Hence the studies on electrophotographic organic photoreceptors are still being continued. For example, one can find from the recent literature novel hydrazone compounds (JP-A-8-143550), carbazole type stilbene compounds (JP-A-8-59615 and JP-A-9-295969), and tri-substituted ethylene compounds (JP-A-63-225660, JP-A-5-181292, JP-A-9-59256, and JP-A-10-59952).
U.S. Pat. No. 4,539,507 to VanSlyke et al. discloses that a multi-layer type organic luminescent element having a hole-injecting and transporting zone comprising an aromatic tertiary amine containing a phenyl group, a phenylene group or a biphenylene group exhibits stabilized light output and thereby a prolonged service life. To further improve the light output stability, efforts have been made by many researchers to add improvements to the aromatic tertiary amines to be used in the hole-injecting and transporting zone, resulting in a large number of patent applications and reports in the professional literature. For example, improvements on biphenyl type tertiary amines are found in Japanese Journal of Applied Physics, vol. 27, L269 (1988), JP-A-59-194393, Appl. Phys. Lett., vol. 66, p. 2679 (1995), JP-A-5-234681, JP-A-7-331238, JP-A-8-48656, and WO95/09147; and improvements on star burst type tertiary amines are disclosed in Appl. Phys. Lett., vol. 65, p. 807 (1994), and JP-B-7-110940. However, the compounds known from the literature cannot be said to have sufficient performance, still leaving room for further improvement.
An object of the invention is to provide a luminescent element material and a luminescent element that emit light of high brightness at a low driving voltage and exhibit excellent durability when used repeatedly.
Another object of the invention is to provide a novel ethylene derivative useful in an electrophotographic photoreceptor, an organic luminescent element, and the like.
A further object of the invention is to provide a novel ethylene derivative useful in an electrophotographic photoreceptor or an organic luminescent element and excellent in charge transporting ability and storage stability.
A still further object of the invention is to provide a benzoazepine derivative having a vinyl group which can be a raw material of polymer useful as an electrophotographic photoreceptor or an organic luminescent element.
The above objects of the invention is accomplished by the following means.    (1) A luminescent element material comprising a polymer having a partial structure represented by formula (I):     (2) A luminescent element material comprising a polymer having at least one repeating unit represented by formula (II): wherein R2c, R2d, and R2e each represent a substituent; 2p, 2q, and 2r each represent an integer of from 0 to 4; where 2p, 2q or 2r is 2 or greater, two or more R2c's, R2d's or R2e's may be the same or different; L2 represents a single bond or a divalent linking group; R21 represents a hydrogen atom, an alkyl group or an aryl group; and m2 represents an integer of 1 or greater.    (3) A luminescent element material comprising a polymer containing at least one repeating unit represented by formula (III): wherein R3e represents a hydrogen atom or a substituent; R3c, R3d, and R3f each represent a substituent; 3p and 3r each represent an integer of from 0 to 4; 3q represents an integer of from 0 to 3; where 3p, 3q or 3r is 2 or greater, two or more R3c's, R3d's or R3f's may be the same or different; L3 represents a single bond or a divalent linking group; R31 represents a hydrogen atom, an alkyl group or an aryl group; and m3 represents an integer of 1 or greater.    (4) A luminescent element material comprising a polymer having at least one repeating unit represented by formula (IV): wherein R4e represents a hydrogen atom or a substituent; R4c, R4d, and R4f each represent a substituent; 4p and 4q each represent an integer of from 0 to 3; 4r represents an integer of from 0 to 4; where 4p, 4q or 4r is 2 or greater, two or more R4c's, R4d's or R4f's may be the same or different; L4 represents a single bond or a divalent linking group; and m4 represents an integer of 1 or greater.    (5) The luminescent element material according to (2) above, wherein m2 in formula (II) is 6 to 100,000.    (6) The luminescent element material according to (3) above, wherein m3 in formula (III) is 6 to 100,000.    (7) The luminescent element material according to (4) above, wherein m4 in formula (IV) is 6 to 100,000.    (8) An luminescent element comprising a pair of electrodes having therebetween a luminescent layer or a plurality of organic compound thin layers containing a luminescent layer, wherein the luminescent layer or at least one of the plurality of thin layers contains the luminescent element material set forth in any one of (1) to (7) described above.    (9) A luminescent element comprising a pair of electrodes having therebetween a luminescent layer or a plurality of organic compound thin layers containing a luminescent layer, wherein the luminescent layer or at least one of the plurality of thin layers is a layer formed by coating with the luminescent element material set forth in any one of (1) to (7).    (10) An ethylene derivative having a nitrogen-containing 7-membered ring as represented by formula (IA): wherein (A) represents an ethylene group, a vinylene group or an o-arylene group; Ar1 and Ar2 each represent an aryl group; R1 and R2 each represent an alkyl group or an aryl group; R3 represents an alkyl group or an aryl group; R4 and R5 each represent a halogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a dialkylamino group, an N-alkyl-N-arylamino group or a diarylamino group; Ar1 and R1, or Ar2 and R2 may be taken together either directly or indirectly to form a ring; Ar1(R1)C═CH—(CH═CH)m— and Ar2(R2)C═CH—(CH═CH)n— are on the 2- and 3-positions and the 7- and 8-positions of the respective benzene rings; m and n each represent an integer of from 0 to 2; and p and q each represent an integer of from 0 to 3.    (11) A benzoazepine derivative represented by formula (IB): wherein (A) represents a vinylene group or an o-arylene group; R1, R2, R3, Y1, Y2, and Y3 each represent a hydrogen atom or a substituent, provided that at least one of Y1, Y2, and Y3 represents an ethenyl group; n represents an integer of from 1 to 4; when n=0, Y3 represents an alkyl group, an aryl group or an ethenyl group.